Process for producing colored photographs



I as

Patented Apr. 5, 1927;

UNITED *s'rArss- ERNST AUGUST LAGE, 0F HAMBURG, GERMANY.

PATENT OFFICE.

PROCESS FOR PRODUCING COLORED PHOTOGRAPHS (POSITIVE PBTNTS ON PAPER OR THE LIKE).

No Drawing. Application filed July 25, 1921, Serial No. 487,527, and in Germany July 30, 1920.

This invention relates to a process for producing color prints on paper in nonfading colors by treating a sllver black print from the part negative for the yellow print in a series of independent success ve steps for developing the colors in the print to produce a final colored image s milar to the object in nature I The process includes the treatment of the print in a bleaching bath, a ferricyanid process to produce the blue portion of the light paper or the like is produced from the negative which is used for the yellow print. The silver black print is fixed and washed, and after fixing and washing, is introduced into a bleaching bath, the composition of which is substantially as follows:

Cubic centimeters. 10% lead nitrate 15 10% potassium ferricyanide solution 10 10% nitric acid solution 1 Distilled water 75 After the bleaching is completed, which changes the silver image of the print into a fading image, the print is thoroughly washed until the image no longer looks yel lowish, and then dried. After the drying of the print, the print is moistened in subdued light by means of a cotton wool pad, with a solution consisting of:distilled water, cbc. -cm.; ferric ammonium citrate, 7 gr.; potassium ferricyanide, 4 gr.

The paper thus coated and dried is now printed under the partial negative intended for the blue-print, until the ima e becomes clearly visible. The printing wit a normal is carried out as .print is uniformly coated with a 3% solution of potassium bichromate. After the drying, the print which is so far ready, is placed under the partial negative for red printing, and the printing is continued until the image becomes just visible in the brightest portions. The print is then rinsed, again, until the water running off is no longer yellowish, and placed on a flat support and properly dried. By completing the part negative for the red print on the paper rendered sensitive with the solution of potassium bichromate, the gelatine of the gas light paper is more or less tanned according to the influence of the light. By soaking in water a weak relief is then formed. Now, when the picture is rolled or dotted With red fat color, such color adheres only to those places which have been exposed to the light, and the result is the red part picture. After the bleached silver picture with the solution of potassium bichromate has been rendered sensitive to the light for the red part picture, the bleached silver picture is at the same time changed 3 into a picture in oil. After a short fixing in sodium thiosulfate and subsequent rinsing and drying, the color image is ready It is especially important in the present process to keep the yellow partial image in invisible state until the blue and the red partial images have been printed.

Another advantage is that the bichromate solution s read on the print for the purpose of o taining' the red partial image,

simultaneously develops the yellow partial ima e.

Wat I claim is: a A process producing colored photographic no i prints, consisting in subjecting a black silver print made from the yellow printing negative to a bleaching bath including lead nitrate, potassium ferricyanide, and nitric red printing print, applying red color for acid, resensitizing the print wlth a solution adherence, to those parts of the negative containing potassium ferricyanide and ferwhich have been exposed to the light, and 10 ric ammonium citrate and printing from the fixing the sodium thiosulfate. 6 blue printing negative, washing and then In testimony whereof I aflix my signature.

resensitizing the print with a solution of potassium bichromate, printing from the ERNST AUGUST LAGE. 

